1. Field of the Invention
This invention relates broadly to surgical instruments. Particularly, this invention relates to flexible endoscopic instruments for use through an endoscope. More particularly, this invention relates to a surgical clip applier which is adapted for use through an endoscope and may be used to clamp and/or suture, ducts, vessels, and other tissues, to anchor a tissue, or to attach a foreign body to a tissue.
2. State of the Art
Surgical clips are generally used to apply clamping force to ducts, vessels, and other tissues. In addition, surgical clips are particularly useful in controlling bleeding of a tissue in lieu of suturing or stapling where suturing or stapling is difficult.
All of the currently available surgical multi-firing clip appliers are substantially rigid devices intended to extend through a trocar port or through an incision to a surgical site requiring application of a clip. The devices have been rigid because a stiff pushing element has been required in order to exert the required pushing force to move the clip over the tissue.
However, there is a substantial need for a flexible clip applier, particularly one insertable through a lumen of an endoscope. The ability to apply clips through an endoscope would permit myriad minimally invasive surgical solutions to medical problems, especially those of the gastrointestinal tract. However, it is accepted theory that the transmitted force required to advance or form a clip over tissue cannot be produced in the distalmost end of a long flexible device that is commonly constructed with a metal tubular coil, or polymer tube, such as an endoscopic device or catheter. For example, C. Paul Swain, MD, a recognized expert in endoscopic instruments and particularly endoscopic stapling devices, has stated that “[i]t is hard to exert more than 200 g of force on the tissue when pushing. . . . This fact is of course one feature that makes intervention at flexible endoscopy relatively safe”. See C. Paul Swain, “What Endoscopic Accessories Do We Really Need?”, Emerging Technologies in Gastrointestinal Endoscopy, Gastrointest. Endosc., Vol. 7, No. 2, pp. 313–330 (April 1997). Yet, a pushing force substantially greater than 200 g is required to push a clip over compressed tissue. In fact, it is believed a force in excess of 500 grams (1.1 lbs) is required for a satisfactory instrument, and substantially greater forces, e.g., in excess of 1500 grams (3.3 lbs) would be desirable.
Generally a flexible endoscopic device (e.g., a biopsy forceps device) includes an outer tubular member, typically being constructed of a metal tubular coil or a polymer tube which is poor in transmitting forces that impart tensile stresses to the outer tubular member, a control element longitudinally movable relative to the tubular member, an end effector coupled to the distal ends of both the tubular member and the control element such that relative movement of the control element and the tubular member causes operation of the end effector, and a handle which moves the control element relative to the handle.
This type of flexible endoscopic instrument is limited in the amount of pushing force it can generate for several reasons. Compression of a flexible control element (pushing element) tends to cause the pushing element to buckle within the outer flexible sheath of the device. If a relatively larger diameter flexible pushing element is used such that it better resists buckling, the pushing element may impart too much stiffness to the flexing of the endoscopic instrument. In addition, a flexible pushing element of larger diameter is subject to greater frictional forces within the outer sheath which reduces the force transmitted from the handle to the end effector. If the flexible pushing element is made relatively smaller in diameter, it is subject to kinking which will result in little to no force transmitted to the distal end. Kinking is especially a problem in endoscopic instruments, as the endoscope and its lumen may be extended through a tortuous path. For these reasons and others, mechanical application of a relatively large distal end pushing force and particularly clip application have been absent from the capability of flexible endoscopic tools.
In addition, it is important that the tissue about which a clip is to be applied be substantially compressed. While the jaws apply a clamping force which compresses the tissue, large clamping forces are difficult to achieve due to the dimensions of the relatively small jaw assembly. That is, the dimensions are such that the lever arm between a pivot of the jaw assembly and each jaw tang is relatively short, limiting the mechanical leverage on the jaw assembly.